Yesterday's 7:30 to tomorrow is how many hours

7:30 p.m. to 7:30 a.m. exactly twelve hours,

assuming that seven thirty just finished dinner, then we can go out for a walk, square dancing ah, etc., nine thirty home to sleep, sleep to seven in the morning to get up, and then eat breakfast, on the seven-thirty, then just is twelve hours, eight o'clock we can go to work.